Cyber Resilience

CVE-2026-6757

Memory Safety in Mozilla Firefox ≤ 140.10.0

Published
21 April 2026
Modified
22 April 2026
Patch / advisory
CVSS Score v3.1 6.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
EPSS Score 0.0029 22th percentile
Risk Priority 48 floored blend · peak EPSS

Summary

CVE-2026-6757 is a medium-severity Access of Uninitialized Pointer (CWE-824) vulnerability in Mozilla Firefox. Its CVSS base score is 6.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 22th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-6757 is an invalid pointer vulnerability (CWE-824) in the JavaScript WebAssembly component of Mozilla products. It affects Firefox versions prior to 150, Firefox ESR prior to 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. The issue stems from an access of an uninitialized pointer, which can lead to memory corruption when processing malicious WebAssembly content.

The vulnerability has a CVSS v3.1 base score of 6.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L), indicating that an unauthenticated remote attacker can exploit it over the network with low complexity but requires user interaction, such as visiting a malicious website or opening a crafted email in Thunderbird. Successful exploitation could result in limited impacts, including disclosure of sensitive information, minor modification of data, or partial denial of service due to application crashes or corruption.

Mozilla security advisories (MFSA 2026-30 through 2026-34) and the associated Bugzilla entry (bug 2013588) confirm the issue was addressed in the listed fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk, as no workarounds are specified in the provided references.

EU & UK References

Vulnerability Data

Invalid pointer in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-2785Same product: Mozilla Firefox
CVE-2026-16409Same product: Mozilla Firefox
CVE-2026-2805Same product: Mozilla Firefox
CVE-2026-6748Same product: Mozilla Firefox
CVE-2026-6751Same product: Mozilla Firefox
CVE-2026-6749Same product: Mozilla Firefox
CVE-2026-6778Same product: Mozilla Firefox
CVE-2026-16353Same product: Mozilla Firefox
CVE-2025-1016Same product: Mozilla Firefox
CVE-2024-6615Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 140.10.0 · ≤ 150.0
mozilla
thunderbird
140.0 — 140.10.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

Developer testing and evaluation can discover uninitialized pointer accesses through static analysis, dynamic testing, or fuzzing before deployment.

Requiring documented development processes and tools enables use of analyzers or coding standards that identify uninitialized pointer defects.

Security engineering principles can mandate memory-safety practices and language choices that structurally avoid uninitialized pointer use.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly prevent uninitialized pointer bugs via coding standards, analysis, and reviews, but eliminating this single weakness only partially fulfills the broader control.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

finds

Security testing can detect uninitialized pointer usage before release.

prevents

Secure development life cycle mandates practices that reduce uninitialized pointer defects.

degrades

Application security requirements can specify pointer initialization rules.

degrades

Secure architecture principles discourage unsafe pointer handling.

prevents

Secure coding standards directly prohibit use of uninitialized pointers.

References